Numerical Evaluation of Residual Stress Relaxation by Cyclic Load

The aim of this work is to evaluate by numerical simulation the real stress state of a welded component subjected to a sinusoidal external load. In particular, the relaxation process of the residual stress, due to the application of a cyclic external load, has been studied. Longitudinal welded joints, laser welded and 3mm thick, are analysed in this work following the residual stress evolution during a fatigue test. A numerical procedure, implemented by ABAQUS code, carries out the residual stress field originated by a welding process and it is taken as a pre-stress condition in the present ABAQUS simulations. In order to evaluate the influence of the amplitude level on the residual stress relaxation, eight different sinusoidal loads at the load ratio R=0.1 are applied to the model. The results show a significant reduction of the initial residual stress level even after the first load cycle and they offer a very precise explanation of the fatigue behaviour of this kind of welded joints, confirming the behaviour experimentally observed.